The bumble bee microbiome increases survival of bees exposed to selenate toxicity

Abstract

Summary Bumble bees are important and widespread insect pollinators who face many environmental challenges. For example, bees are exposed to the metalloid selenate when foraging on pollen and nectar from plants growing in contaminated soils. As it has been shown that the microbiome of animals reduces metalloid toxicity, we assayed the ability of the bee microbiome to increase survivorship against selenate challenge. We exposed uninoculated or microbiota‐inoculated Bombus impatiens workers to a field‐realistic dose of 0.75 mg l−1 selenate and found that microbiota‐inoculated bees survive slightly but significantly longer than uninoculated bees. Using 16S rRNA gene sequencing, we found that selenate exposure altered gut microbial community composition and relative abundance of specific core bacteria. We also grew two core bumble bee microbes – Snodgrassella alvi and Lactobacillus bombicola – in selenate‐spiked media and found that these bacteria grew in the tested concentrations of 0.001–10 mg l−1 selenate. Furthermore, the genomes of these microbes harbour genes involved in selenate detoxification. The bumble bee microbiome slightly increases survivorship when the host is exposed to selenate, but the specific mechanisms and colony‐level benefits under natural settings require further study.

The direct and indirect effects of environmental toxicants on the health of bumble bees and their microbiomes

“…We pooled 5 μL of each normalized library and performed a final clean up with a single column PureLink PCR Purification Kit, then sequenced the multiplexed libraries using a V3 Reagent Kit at 2 × 300 cycles on an Illumina MiSeq Sequencer in the UC Riverside Genomics Core Facility. Raw sequencing data are available on the NCBI Sequence Read Archive (SRA) under accession numbers SRR6788889 - SRR6789022, and microbiome data of selenate versus control treatments were previously published in Rothman et al 2019 (53).…”

“…For example, host-associated bacteria have been shown to detoxify chromium and lead (49), copper (50), arsenic (51), and selenite (52), mainly through accumulation or respiration. Specifically in bees, the microbiome has been shown to reduce selenate-induced mortality (53), and bee-associated microbes removed cadmium from their environment (22), although the mechanisms for microbe-mediated protection against toxicants in bees remains largely unknown. As bacterial genes often encode metal(loid) transporters and detoxification pathways, we may be able to understand toxicant-protection mechanisms by annotating the pathways in symbiont genomes.…”

Community assembly of the native C. elegans microbiome is influenced by time, substrate and individual bacterial taxa

“…This conceptual framework should also apply to the microbiome, and thus help us understand microbiome composition and the resulting functions and effects on host biology. For example, members of the microbiome can support nutrient uptake (Warnecke et al ., ; Keeney and Finlay, ), detoxification (Chaucheyras‐Durand et al ., ; Rothman et al ., ) and pathogen removal inside a host (Fraune et al ., ; Dirksen et al ., ; Kwong et al ., ; Kissoyan et al ., ). Additionally, a diverse community is generally more resilient to disturbances (Holling, ), which also seems to apply to microbiomes (Greenhalgh et al ., ; Sommer et al ., ).…”

Spotlight on how microbes influence their host's behavior

“…Although usually applied to animals rather than plants or microbes, this definition of ‘behavior’ encompasses all types of organisms and their populations. Indeed, besides articles on animal hosts (Koehler et al ., ; Murfin et al ., ; Truitt et al ., ; Altinli et al ., ; Rothman et al ., ; Zhao et al ., ), this special issue contains a number of research papers devoted to understanding how plants respond to their microbial inhabitants. Among these studies on plant–symbiont interactions, several focus on plant responses to nitrogen‐fixing bacteria (Lamouche et al ., ; Baena et al ., ; Bañuelos‐Vazquez et al ., ; Pujic et al ., ; Songwattana et al ., ), while others investigate endophytes and their role in alleviating plant abiotic stress (Vigani et al ., ; Lanza et al ., ; Llorens et al ., ).…”

“…Furthermore, a fungal and bacterial endophyte are both reported to lead to higher plant abiotic stress tolerance: the fungal endophyte by expressing its own salt-detoxifying ion pumps (Lanza et al, 2019), and the bacterial endophyte by stimulating the activity of proton pumps encoded in its host's genome (Vigani et al, 2018). Selenium toxicity is another type of abiotic stress and the bumblebee microbiota is shown to contribute to promoting its host survival in conditions of selenate exposure (Rothman et al, 2019).…”